This invention was made in the course of, or under, a contract with the Energy Research and Development Administration. It relates generally to the art of centrifugal separation of blood components.
In a continuous flow blood centrifuge, whole blood enters the centrifuge rotor and is centrifugally separated into three zones within the separation chamber of the rotor, the plasma zone, the white cell zone, and the red cell zone. All of the zones contain some plasma, so each zone is sufficiently fluid to be separately removed from the rotor by pumps. It is the continuous separate extraction of the zones which is the critical consideration in continuous flow blood centrifuges. In the type of centrifuge disclosed in the above-identified commonly assigned copending application, the three zones are separated at the interface by fluid splitting means such as blades. The red cell zone is removed by a fluid splitter blade positioned at the interface between the white cell zone and the red cell zone. The separation chamber is inclined outwardly to aid in the flow of red cell rouleaux (aggregates) along the outer wall of the chamber.
A critical concern in continuous flow blood centrifuges is the position of the interfaces between separated zones. As may be seen by the calculations in the above copending application, the exact design configuration of a particular centrifuge rotor depends upon the properties of the blood to be separated. More particularly, the radial position of the first annular fluid splitting means and the angle of inclination of the separation chamber depend upon, among other things, the hematocrit of the entrant whole blood. Hematocrit being the ratio of the total volume of particles in blood to the total blood volume, it is easily seen that the widths of the separated zones within the centrifuge depends directly upon the hematocrit of the entrant whole blood. It is somewhat impractical to construct a different centrifuge for each range of hematocrit values, so a method of adapting existing centrifuges to a wide range of hematocrit values has long been needed.